The secretary general of Nato has insisted its Libyan mission does not exceed the UN mandate to protect civilians from Muammar Gaddafi's forces.

Anders Fogh Rasmussen was responding to criticism from the Russian president, Dmitry Medvedev, who on Tuesday claimed the situation in Libya had "already spun out of control" and that the plan to enforce a no-fly zone over the country had been reduced to the straightforward use of force.

Rasmussen said Nato's forces were acting "in strict conformity with both the spirit and the letter of the UN security council motion", which established a no-fly zone and authorised member states to take "all necessary measures ... to protect civilians and civilian populated areas under threat of attack".

The Nato leader admitted he had not yet had any firm offers from any members to "step up to the plate" and offer more precision warplanes, which the Nato commander in charge of Libya requested on Thursday at the start of the meeting of Nato foreign ministers in Berlin.

But, said Rasmussen, "we have indications that nations will deliver what's needed … in the very near future."

A British official said on Friday that the foreign secretary, William Hague, did not see the meeting as a failure, even though it had not prompted any extra member nations to join the French and British-led mission.

"[Hague] never expected to get this sort of commitment overnight. He has been talking to different members and will be following up with them in the days and weeks to come," said the British diplomatic source.

Fourteen of the alliance's 28 members are actively participating in the operation – joined by other nations such as Qatar, the United Arab Emirates and Sweden – and six of them are striking targets in Libya.

The Russian foreign secretary, Sergey Lavrov, has insisted Libya needs a political solution led from within the region, particularly by the African Union, rather than from outside. "There is no magic bullet," he said.

Asked whether Nato should increase its military operation in order to oust Gaddafi, Lavrov said: "The UN has not authorised regime change."